Process for producing sulphates and sulphur



Feb. 26, 1935. c. HARNIST 1,992,572

PROCESS FOR PRODUCING SULPHATES AND SULPHUR Original Filed April 20, 1925 Wm M his Alfie/way I Patented Feb. 26, 1935 PROCESS FOR PRODUCING SULPHATES AND SULPHUR Charles Harnist, Paris, France Application'April 20, 1925, Serial No. 24,681. Re- 'newecl November 1'7, 1933. In Germany April 13 Claims. (Cl. 23-119) I have found that the salts formed by the acsince the simultaneously emitted sulphur dioxide tion of sulphur dioxide, preferably employed in does not es p but influences t e eaction and excess, on ammonia or basic ammonium comhindersthe conversion, if the'temperature and pounds, such as hydroxide, carbonate, sulphide, pressure are not high enough.

5 cyanide in the presence of water and of sul- The polythionates are, at a suific ient tempera- 5 phuretted hydrogen, which ammonium salts ture, transformed inthe following manner: consist of a various mixture of sulphites (acid, normal, or both), thiosulphate, polythionates, in 3(NH4)2S5OS+2H2O=MNHO2sO4+2H2SO4+10s' which the sulphites or the polythionates may be The formation of said salts is particularly difabsent and which must contain at least two ficult, when S02, HzS and NH3 are employed in 10 molecules of oxygen'combinedwith sulphur for the gaseous state and whenQmoreover, as in the one molecule of ammonia (O:HN3=2:1), can be industrial practice, these gases are contained in converted entirely into sulphates (normal and other gases, the S02 being produced by the comeventually acid) and sulphur in the shortest time bustion of sulphur, sulphides of metals (pyrites,

when they are heated under pressure. etc.), hydrogen sulphide, etc., and the H25 and 15 The said salts are obtained by treating solu- NHs being obtained in avery diluted state in the tions, or vapors, or gases containing N113 and distillation gases of coal, lignite and the like. HzS, such as coal distillation gases, the ammonia The preparation of the salts is, accordingly, liquor from it, or vapors resulting from the diselaborated especially in the following descriptill'ation of ammonia liquor and the like with S02 tion. l

or gases or solutions containing it, such as com- One of the difiiculties is due to the partial disbustion gases from sulphur, pyrites, etc., aquesociation of the ammonium salts in the gases, ous solutions of S02 or of acid sulphite or. of hindering the total recovery of NI-Ie and S02. thionates of ammonia and the like. This inconvenience can be obviated by the ad- The conversion of a mixture of sulphites and vantage of the above stated reactions to produce 25 thiosulphate is effected, e. g. according to the refree sulphuric acid (bisulphate) which is used,

action: owing to its non-volatility, to fix the ammonia remaining in the gases, as explained further. fiz f By this method, it is possible-to leave even uncombined ammonia in the gases on purpose, in 30 The conversion of polythionates and thiosulorder to reduce to a minimum the dissociation of phate occurs, e. g. as follows: its salts and the conveyance of S02 by the gases. Another difficulty arises from the necessity of KNEE) 2S5O6+(NH4) Z gg avoiding the lowering of the heating value of the coal distillation "gases bymixing them with the 35 and the conversion of polythionates, thiosulgases containing the S02, while employing, neverphate and sulphites y the reaction; theless, always the same liquor for the treatment 5 (NHU 2S3O6+3 (NHD 2S2O3+2NH4HSO4+ of both, in order to obtain a concentrated solution 2(NH zSO31l(Nl-I4) 2SO4+2H2SO4+11S of the ammmmm Salts' 40 This difficulty may be easily surmounted by 40,

These various mixtures depend on the proscrubbing the two gases separately and alternately portion of the hydrogen sulphide to the ammonia with the liquor. But, it is also possible to effect a and sulphur dioxide. simultaneous treatment by causing the two gases In the polythionates, this proportion is the to pass through an apparatus filled withthe liquor highest possible for the hydrogen sulphide and through, e. g a saturator and by separately 001- 45. sulphur dioxide, and in the neutral sulphide, the lecting the gases in the usual manner the S02 lowest (=0 for the H28). containing gas, the amount of which is much The conversion of polythionates into sulphate lower, being introduced into :the liquorin a con and sulphur by heating their solution under atfined room, e. g., at the center thereof. and withmospheric pressure is well known. Sulphur didrawn before it leaves'the liquor, through a pipe 50 oxide is freed according to the reaction immersed in the liquid, while the Nliscontaining gas traverses the rest of the liquor and is dis- (NH) 2s5o6 (NI-I4) 2SO4+SO2+3S charged from its surface for further treatment.

The reaction will, however, proceed differently After the treatment in the saturator, the S02 i when heating the said solution in a closed. Vessel, gas isfreed from the remaining .502. in one,

or several, apparatus (scrubbers or saturators), which are directly compounded by a by-pass with the S02 gas before its inlet in the saturator, in order to regulate the admission of S02 to the latter.

The treatment in the said apparatus is efiected with the solution of the saturator, to which solution ammonia liquor and the wash water from sulphate may be added, or with the solid salts formed in the saturator and withdrawn and dissolved in ammonia water.

From the thus acidified solution, a portion is,

preferably, constantly withdrawn to be converted into sulphate, sulphur and free sulphuric acid by heating under pressure. free sulphuric acid may be regulated by the amount of S02 absorbed by the solution before its conversion, the excess being diminished by adding some solution from the saturator.

The converted liquor, after having been separated from the sulphur, is then employed to recover, with the free sulphuric acid contained, the ammonia retained in the NI-Ia gas leaving the saturator, which operation may be efiected in a second saturator, in which the solution may be evaporated in any known manner, e. g., by heating the gas before its admission therein, while the crystalized usual.

Instead of the coal distillation gases, the gases or vapors from the distillation of ammonia liquor may be employed.

The aforementioned separate and alternate treatment of the two gases in scrubbers requires more and larger apparatus, but less power for circulating the gases. One, or several scrubbers may be used, and, eventually, a saturator.

The wash liquor circulating from the S02 gases to the NH; gases may be maintained acid or, preferably, semi-neutral (one: molecule normal and one molecule acid salt)by mixing with the liquor from the NH3 gases treatment in order to avoid the transfer of S02 into the NH: gases. If it is desired to leave uncombined NHz in the latter, the admission of the wash liquor into the scrubber must be suitablylimited. A portion of the liquor from the'S02 treatment is also in this case, withdrawn for the conversion and the consulphate may be brought out, as

verted liquor used to recover the NHs notabsorbed in the NH3 gases, which recovery may be effected in a saturator or in, a scrubber. The solid sulphate may be recovered by evaporation in any well known manner. 1

., By using several apparatuse. g., two or more stages, for the treatment of the NH3 gases, the recovery of the H2S and NH3 gases may be had in accordance with the following, reaction:

which proceeds, as is well known, very slowly and incompletely; It :can, however, be accelerated and completed by the addition of S02.

In order to realize these conditions, the gases or vapors containing NH; and H2S are treated first with more S02 than is necessary to decompose the H28; then, in a second treatment, the excess S02 is removed with NHs, preferably, also in excess, and may be finally recovered in any known manner, preferably, by thefree sulphuric acid of the converted solution, as above'stated.

Referring to the accompanying flow sheet, the NH: gases traverse the set' of scrubbers A1A2 and, thereafter, are led into the saturator 7C. The S0: gases traverse the set of scrubbers The amount of the B1B2, in which they are scrubbed with the wash water of the sulphate discharged from the centrifuge D into the tank E, to which may be added concentrated ammonia liquor. The liquid is systematically circulated in the scrubbers and leaves them sufficiently acidified to be sent into the scrubber A1, and, thence, being partly neutralized by the NHs of the gases, a part is conducted into scrubber A2, to which ammonia liquor, or vapors and gases from its distillation, may be added. If the ammonia liquor or condensed ammonia vapors are employed, it may also be directly added to the liquor from the first scrubber. The liquors are then returned to the scrubber B1 and when they have become sufiiciently concentrated by this alternate circulation, a portion of the acidified solution leaving this scrubber is pumped into the pressure vessel F, which is steam heated. The solution thus converted into sulphate and sulphur descends through the expansion vessel H into the'tank I, inwhich it is separated from the sulphur, and then into the saturator C, in which-it is evaporated by theNHa gases previously heated, after having absorbed the remaining NH3 from the gases. Sulphuric acid produced in accordance with known processes, such as the waste sulphuric acid from the purification of benzol, may be added into the saturator from time to time to increase the acidity.

The acidity of the solution may, as above described, also, in this example, be regulated and, if desired, reduced to 0 by the content of S02 before the conversion, adding to the acidified solution neutral or ammoniacal liquor from the scrubbers A1 or A2. The recovery of the remaining ammonia and the evaporation may be effected by any desired manner other than through the saturator. The method with the saturator, allowing the simultaneous recovery and evaporation, is, however, preferred under the conditions of the process which-permit, by acidifying sufficiently, the liquor arising from the S02 scrubbers to'produce sulphuric acid by heating, under pressure, the best absorption of ammonia. A saturator may, also, be employed instead of scrubber A1. saturator will allow the simultaneous treatment of the S02 and of the NHs gases, as above described. But, in this case, also, a final recovery of the S02 will be necessary through one or two scrubbers whose volume is to be reduced in accordance with the first absorption of S02 in the saturator. On the other side, the saturator will require more power for conducting the gas therethrough.

If the complete removal of H2S and I-ICN is not desired, the second scrubber may be omitted. The admission of the washing liquor is then to be limited in order notto absorb the Whole ammonia, which is removed in'the saturator C.

The cyanogen of the gas is fixed in a known manner as sulphocyancornpound by the sulphur formed in the scrubber A1 by the reaction between S02 and H253 and pumped with the wash liquor into scrubber A2. This sulphocyanate is also converted by heating the solution, under pressure, into sulphate and sulphur by a well known reaction with the sulphuric acid formed. H nosufficientammonia liquor is available, the NH3.gases are divided into two parts, of which one is charged in the first scrubber with an excess of S02, then removed in the second scrubber by the NHs and the H28 of the other part, then reunited with the first part in the scrubber, the circulation of the wash liquor and the This l 1,992,572 being the I is promoted by the presence of water, and the latter will also act to isolate from the reaction the CO2, which is usually contained in the coal gases, by dissolving the S02 and H28, the CO2 being but slightly soluble. The water may be introduced into the gases in a finely divided state, or may be produced by the condensation of steam, which is already present in the gases, or may be introduced into them.

These treatments may also be effected by the use of hot gases before removal of the tar therefrom, or the tar, in order to preserve the heat of the gases, may be removed at a high temperature above the dew point. Herein, the temperature in the first scrubber may exceed C., in the second it should be 100 C., but without deccnding much below the dew point, which condition is also to be observed for the saturator C.

Instead of gases from the distillation of coal, any other gas or vapor containing NH: or H25 or both may be employed. If only me is present, the NI-Ia may be added.

The conversion of the ammonium salts formed according to the above disclosed methods into sulphate and sulphur by heating under pressure is efiected by conducting the abtained solutions, preferably, in a continuous manner through the pressure vessel by pumping through the closed vessel while continuously heated. The latter may be provided with a stirrer and steam jacket, or a coil in the usual manner. 'I have found that it is more advantageous to introduce steam directly into the closed vessel, preferably, through one or more circular tubes with several tangential branches open at the ends. The steam issuing from these tangential branches will give the liquid a rotary motion and will replace the known stirrers to advantage. This makes the reaction uniform, and will further serve to collect the sulphur into drops by the high speed of rotation and to prevent the entering solution, at once, leaving the vessel. At the outlet of the vessel a strainer device may be applied, which causes the sulphur to issue in the form of drops and distributes same upon the strainer in order that sulphur, which is still in the finely divided state, may be retained and agglomerated. To prevent the sulphur from solidifying in the outlet, a steam tube is branched from the circular tube and leads through the strainer to the opening. The steam may, also, serve wholly or partly to heat the solution to the temperature needed by the reaction and is continuously adduced when the solution is conducted continuously through the vessel.

In this manner, the conversion of the said solutions containing thionates, which may be mixed with sulphites, will take place even below C., but it may be accelerated by heating above 150 C. The heat which is to be supplied depends upon the concentration of the solution and the percentage of sulphurous acid.

To obtain the. solid sulphate and the sulphur, the converted solutions may then be treated in the above described manner.

I claim as my invention:--

1. The process of producing sulphates phur by 'intramolecular transformation which consists in heating under pressure a solution obtained by the action of sulphur dioxide on ammonia and its basic compounds forming ammo nium sulphites and thionates, in the presence of water and of sulphuretted hydrogen.v

2. The process of producing sulphates and sulphurby intrainole'cular transformation which consists in heating. under pressure a solution obtained by the action of sulphur dioxide on ammonia and its basic compoundsforming ammonium sulphitesand thionates, in the presence of water and ofsulphuretted hydrogen. the solution being heated by introducing steam directly into it. 1 v

3; The process ofproducing sulphates and sulphur. by viirtramolecular transformation which consists in heating under pressure a solution ob-' tained by the action of sulphur dioxide on ammonia and its basic compounds formingammm nium' sulphites and thionates, in the presence of' water and of sulphuretted hydrogen, the solution being heated by introducing steam thereinto in such manner as to give the liquor a rotary 'mo- 4. The process of producing sulphates and sulphur by intramolecular transformation which consists in heating under pressure a solution ob-' tained by the action of sulphur dioxide on ammonia and its basic compounds forming ammoniumsulphites and thionites, in the presence of water and of sulphuretted hydrogen, the solution being heated by introducing steam thereinto in such manner as to prevent the sulphur from solidifying at the outlet of the closed vessel.

5. The process of producing sulphates and sulphur by intramolecular transformation which consists in heating under pressure a solution obtained by the action of sulphur dioxide on ammonia and its basic compounds forming ammonium sulphides and thionates, in the presence of wa-" ter and of hydrogen sulphide, while the solution is conducted continuously through the closed vessel.

6. The process of producing sulphates of ammonia and sulphur by intramolecular reaction, which consists in heating, under pressure, solutions obtained by the action of sulphur dioxide, in the presence of water and of hydrogen sulphide upon ammonia containing gases, the addiand su1-- tion of free sulphur dioxide to the gases being limited in order that the gases retain ammonia, and recovering the ammonia by a further treatment in any known manner.

7. The process of producing sulphates and sulphur by intramolecular transformation which consists in heating under pressure solutions obtained by scrubbing coal distillation gas containing ammonia and hydrogen sulphide with water, acidifying the latter separately with sulphur dioxide for again scrubbing the gas, in a cycle, until it becomes sufiiciently enriched with the thus,

formed salts (sulphites, thionates) for the said transformation, to which the solution is continuously conducted after the acidification and replaced in the scrubbing by water.

8. The process set forth in claim 7, wherein the scrubbing of the gas is effected by limiting the admission of the acidified solution in order to leave some ammonia in the gas avoiding the presence of sulphur dioxide in the latter, this ammonia then being removed in a further treatment in any suitable manner.

9. The process of producing sulphates and sulphur by intramolecular transformation, which consists in heating under pressure solutions obtained by scrubbing coal distillation gas containing ammonia and hydrogen sulphide with water, acidifying the latter separately with sulphur dioxide for again scrubbing the gas, in a cycle, until it becomes sufiiciently enriched with the salts thus formed (sulphites, thionates) for the said transformation, to which the solution is conducted continuously after the acidification, the scrubbing being effected in three stages; first by a sufiicient admission of the acidified solution for the complete removal of the ammonia and hydrogen sulphide; in the second stage by some solution from the first scrubbing with'the addition of ammonia and water in order to remove the acid compounds from the gas and to communicate to the latter some ammonia, recovered in the third treatment in any suitable manner.

10. The process set forth in claim 9, wherein the ammonia is recovered in the third stage with the transformed sulphate solution containing free sulphuric acid.

- 11. The process according to claim 9, wherein the ammonia is recovered in the third stage with the transformed solution to which sulphuric acid is added.

12. The process set forth in claim 9, wherein the ammonia is recovered in a saturator traversed by the gas, the crystallized sulphate being obtained by evaporating the solution by the gas preheated and by ejecting the salt in a suitable manner.

13. The process set forth in claim '7, wherein the scrubbing of the gas is effected in three stages, first by a sufficient admission of the acidified solution for the complete removal of the ammonia and hydrogen sulphide, the gas, in order to accelerate the reaction between H25 and S02, being passed through an electric field before the second stage, which is effected by some solutionfrom the first scrubbing with the addition of ammonia in order to remove the acid compounds from the gas and to communicate to the gas some ammonia, recovered in the third treatment.

CHARLES H ARNIST. 

